Polyol extended cathodic electrodeposition resins

Abstract

An improved electrodepositable cationic resin is disclosed. Prior art electrodepositable cationic resins are formed from polyepoxides which are chain extended with polyether or polyester polyols to internally flexibilize the resin. The polyepoxide resin of the invention is chain extended with a monoepoxide-triol adduct which provides a resin with improved throw power and improved flow while maintaining other important characteristics of the resin.

We claim: 
     
       1. An improved cationic electrodeposition resin wherein the resin is made by chain extending an aromatic polyepoxide with an internal flexibilizer; wherein the improvement comprises said internal flexiblizer consisting of a monoepoxide-triol adduct. 
     
     
       2. The resin of claim 1 wherein said polyepoxide is a polymer containing about two epoxy groups per molecule. 
     
     
       3. The resin of claim 2 wherein said polyepoxide is a polyglycidyl ether of polyhydric phenol. 
     
     
       4. The resin of claim 1 wherein said monoepoxide-triol is the reaction product of a monoepoxide and a triol. 
     
     
       5. The resin of claim 4 wherein said monoepoxide is selected from the group consisting of an alkyl glycidyl ether or an alkyl glycidyl ester. 
     
     
       6. The resin of claim 4 wherein said triol is selected from the group consisting of trimethylol propane or trimethylol ethane. 
     
     
       7. The resin of claim 1 wherein the molar ratio of monoepoxide to triol is about 1:1 to 1:3. 
     
     
       8. The resin of claim 1 wherein the aromatic polyepoxide has at least two epoxy groups per molecule and is a polyglycidyl ether of a polyhydric phenol and the flexiblizer is the reaction product of a monoepoxide of an alkyl glycidyl ether and a triol of trimethylol propane wherein the molar ratio of monoepoxide to triol is about 1:1 to 1:3. 
     
     
       9. A method of coating an electrically conductive article with the resin of claim 1, comprising: (1) mixing said resin with an amine to form a polyepoxy amine adduct;   (2) blending said adduct with an acid, crosslinker, and water to form a principal emulsion;   (3) adding more water and pigment paste to the principal emulsion thereby forming an electrocoat bath;   (4) immersing the article in the electrocoat bath; and   (5) passing a direct current through the article.